Material-handling boom having straight line motion



Nov. 26, 1968 R. L. TWEEDALE 3,412,330

MAIERIAL'HANDLING BOOM HAVING STRAIGHT LINE MOTION Filed Nov. 8, 1966 Zmm mm L W m A TTOK/VEKF.

rate

ABSTRACT OF THE DISCLOSURE The disclosure is concerned with materialhandling booms, and particularly with booms for excavators of the typecommonly referred to as backhoes. A boom is mounted on a tractor mountedsupporting frame in such a manner that it can move upwardly anddownwardly as well as from side to side relative to the frame. Pivotallymounted on the free end of the boom is a dipper stick which carries atits free end an excavating bucket. The boom and dipper stick arefoldable and unfoldable relative to each other such that the bucket canbe extended away from and retracted toward the supporting frame forexcavating. Operation of the boom, dipper stick and bucket isaccomplished hydraulically. Compensating mechanism is incorporated intothe boom assembly to cause the bucket to move in a straight line path.

BACKGROUND OF THE INVENTION Field of the invention The invention relatesto material handling boom assemblies wherein a material handling memberis movable in various paths relative to a support.

Description of the prior art Conventional backhoes and similar materialhandling apparatus are limited to operation in a curved path since theexcavating bucket moves about the pivotally supported end of the dipperstick, which in turn is pivotally mounted on a boom carried by asupporting frame. An example of such backhoes is disclosed in US.Patent- 3,270,894, Elliott et al., dated September 6, 1966. As aconsequence, such devices are generally limited in their use toexcavating and trenching operations and have been found unsuitable forgrading, contouring and shaping operations.

SUMMARY OF THE INVENTION In accordance with the present invention,compensating mechanism is provided for causing vertical movement of thepivotal support of the dipper stick in a direction opposite to thevertical movement of the bucket as it swings about said pivotal support.As a result, the bucket travels in a straight line path as it movestoward and away from the support upon extension and retraction of theboom assembly. In a preferred embodiment, the compensating mechanismcomprises a compensating cylinder in fluid communication with theactuating cylinder for the boom. The piston of the compensating cylinderfollows the surface of a cam carried by the dipper stick such thathydraulic fluid is pumped into or out of the boom cylinder by thecompensating cylinder in accordance with the angular position of thedipper stick relative to the boom. As the bucket swings downwardly aboutthe pivoted end of the dipper stick the compensating cylinder causes theboom to move upwardly to maintain the bucket in a straight line path,and as the bucket swings upwardly about the end of the dipper stick, thecompensating cylinder causes the boom to correspondingly move downwardlyto maintain the bucket in a straight line path.

atent BRIEF DESCRIPTION OF THE DRAWING The single figure of the drawingis an elevational view of a backhoe embodying the invention with theboom dipper stick and bucket shown in various positions by phantomlines.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawing, a transversesupporting frame 2 is mounted on the rear end of a tractor 4 having rearwheels 6, only one of which is visible in the drawing. Supported onframe 2 is a boom mounting assembly or swing unit designatedcollectively by reference numeral 8. Swing unit 8 may include a supportbracket 10 to which is pivotally connected a boom frame 12, with ahydraulic motor 14 being received between the pivotally connected armsof the bracket and boom frame in a manner disclosed in the abovereferred to Elliott et al. Patent 3,270,894. The boom mounting mayfurther include a rotatable mounting plate 16 for selectively tiltingthe boom about a fore and aft axis of the type disclosed in myco-pending application filed concurrently herewith and entitled,Mounting for Material Handling Masts, Serial Number 592,935, the entiredisclosure of which is incorporated herein by reference.

A boom 18 is pivotally mounted by a pin 20 on the lower end of boomframe 12, and is actuated for vertical pivotal movement about pin 20 bya hydraulic boom actuator in the form of a cylinder 22 pivotallyconnected by a pin 24 with boom 18, and a piston 26 reciprocable incylinder 22 which is pivotally connected at 28 to the boom frame 12.Cylinder 22 communicates with the tractor hydraulic system through hoses30 and 3.1. Admission of fluid into cylinder 22 through hose 30 causespiston 26 to retract into the cylinder and move the boom 18 upwardlyabout pivot point 20. If fluid is withdrawn from the same side of piston26, the piston will extend from cylinder 22 as the boom 18 lowers aboutpin 20.

Pivotally mounted on the free end of boom 18 by pin 34 is a dipper stick32 which is actuated about its pivotal connection with the boom by ahydraulic dipper stick actuator in the form of a cylinder 36 pivotallyconnected at 38 with the boom, and a piston 40 reciprocable in cylinder36 and pivotally connected at 42 with the dipper stick. Carried by thefree end of the dipper stick is an excavating bucket 44 which ispivotally connected at 46 with the dipper stick. Bucket 44 is actuatedabout its pivotal connection 46 by a lever 48 having one end pivotallyconnected at 50 with a dipper stick and its other end pivotallyconnected at 52 with a link 54 projecting from the bucket. The link andlever 54, 48 are actuated by a hydraulic bucket actuator in the form ofa cylinder and piston 56, 6t pivotally connected at 58 with the dipperstick and at 52 with the link and lever 54, 48.

Retraction of piston 40 into cylinder 36, and extension of piston 26from cylinder 22 causes the bucket to move to the extended positionsindicated in phantom lines at A or B in the drawing. Retraction of thebucket toward the supporting frame is accomplished by simultaneousretraction of piston 26 into cylinder 22 and extension of piston 40 fromcylinder 36 in a well known manner to cause the dipper stick to foldtoward the boom. The retracted position is indicated in phantom lines atC in the drawing.

In accordance with the present invention, bucket 44 is caused to move ina straight line path from its extended to retracted positions by meansof a compensating mechanism designated collectively by reference 63. Thecompensating mechanism includes a compensating cylinder 64 mounted onthe boom at 24 and having a piston 66 reciprocable therein with a camfollower 68 on the free end of the piston rod. Cam follower 68 engagesthe surface of a compensating cam 70 secured to the dipper stick byconventional fasteners 72. The configuration of cam 70 is such thatmovement of the dipper stick about pin 34 causes appropriate movement ofpiston 66 into or out of cylinder 64. Cylinder 64 is hydraulicallyconnected with the cylinder 22 by a hose 76 such that as piston 66 isretracted into cylinder 64, hydraulic fluid on the left side of piston66 is forced through hose 76 into cylinder 22 on the side of piston 26causing piston 26 to retract into cylinder 22 and raise boom 18 aboutpivot point 20. Conversely, as piston 66 extends from the compensatingcylinder 64, fluid is withdrawn from cylinder 22 on the side of piston26 causing extension of piston 26 from cylinder 22 and lowering of boom18 about pin 20.

The configuration of cam 70 is such that when the bucket 44 swings in adownward path relative to pin 34, piston 66 is caused to retract intocylinder 64 and force fluid through hose 76 into cylinder 22 in adirection to raise boom 18 about its pivot 20 a distance correspondingto the downward movement of bucket 44. As the bucket starts in an upwardpath relative to pivot pin 34, the configuration of cam 70 is such thatpiston 26 begins to extend from cylinder 64 to cause withdrawal of fluidthrough hose 76 from cylinder 22 and cause piston 26 to extend fromcylinder 22 and lower boom 18 about pivot 20 a distance corresponding tothe upward movement of the bucket relative to pin 34. As a result, pivotpoint 34 moves upwardly about pivot point 20 while bucket 44 moves in adownward path relative to pivot point 34, and pivot point 34 movesdownwardly relative to pivot point 2!} when bucket 44 begins movingupwardly relative to pivot point 34 as it moves past the vertical.Consequently, the resultant path of the bucket is in a straight line asindicated at D and E in the drawing. The initial position of the boom 18is determined by manipulation of manual control levers 78 which in turndetermines the initial working position of the bucket teeth 62 alongpaths D or E, or other straight line paths,

While a specific form of the intention has been illustrated anddescribed, it will be apparent to those skilled in the art that theinvention is not limited to the exact construction shown but that it maytake various other forms without departing from the scope and spirit ofthe invention.

I claim:

1. In material handling apparatus including a support, a dipper stick, amaterial handling member carried by one end of the dipper stick, andmeans mounted on the support pivotally supporting the other end of thedipper stick such that the material handling member is swingable in anarcuate path about said other end of the dipper stick toward and awayfrom the support, the improvement comprising compensating means formoving said one end of the dipper stick vertically in accordance withthe angular position of the dipper stick to cause said material handlingmember to move in a straight line path relative to the support; saidcompensating means including an actuator on said means supporting theother end of the dipper stick operable to cause raising and lowering ofsaid other end of the dipper stick relative to the support, means on thedipper stick operatively engaging said actuator to cause the actuator toraise said other end of the dipper stick during downward travel of thematerial handling member relative to said other end of the dipper stick,and to lower said other end of the dipper stick during upward travel ofthe material handling member relative to said other end of the dipperstick, said actuator including a hydraulic compensating cylinder havinga piston reciprocable therein to cause hydraulic fluid to flow into andout of the compensating cylinder to respectively cause said other end ofthe dipper stick to lower and raise andwherein said means on the dipperstick engaging the actuator i causes the piston to force fluid from thecompensating cylinder as the material handling member moves upwardlyrelative to said one end of the dipper stick, and causes the piston tomove in a direction to cause fluid to flow into the cylinder as thematerial handling member moves downwardly relative to said one end ofthe dipper stick.

2. The construction claimed in claim 1 wherein said means on the dipperstick comprises a cam rotatable about the pivotal support of said otherend of the dipper stick during movement of the material handling membertoward and away from the support, said cam engaging the piston toactuate the piston relative to the compensating cylinder in accordancewith the angular position of the dipper stick.

3. Material handling apparatus comprising a supporting frame, a boompivotally mounted on the supporting frame, a dipper stick pivotallymounted on the free end of the boom, a material handling member carriedby the dipper stick, hydraulic means for actuating the dipper stick topivot relative to the boom and the boom to pivot relative to thesupporting frame to move the material handling member toward and awayfrom the supporting frame, compensating means for causing the hydraulicmeans to move the free end of the boom relative to the supporting frameas the material handling member swings about the free end of the boom ina direction such that the material handling member moves toward and awayfrom the supporting frame in a straight line path, said hydraulic meansincluding a piston and cylinder actuator pivotally connected between thesupporting frame and boom such that the extension and retraction of thepiston relative to the cylinder causes pivotal movement of the boomrelative to the supporting frame, and wherein said compensating meanscauses extension and retraction of the piston in accordance with theangular position of the dipper stick relative to the boom to maintainthe straight line path of the material handling member.

4. Material handling apparatus as defined in claim 3 wherein said boomis pivotally movable relative to the supporting frame in a generallyupward and downward direction, and wherein said compensating meanscauses the boom to move upwardly during downward movement of thematerial handling member relative to the free end of the boom and causesthe boom to move downwardly during upward movement of the materialhandling member relative to the free end of the boom.

5. Material handling apparatus comprising a supporting frame, a boompivotally mounted on the supporting frame, a dipper stick pivotallymounted on the free end of the boom, a material handling member carriedby the dipper stick, hydraulic means for actuating the dipper stick topivot relative to the boom and the boom to pivot relative to thesupporting frame to move the material handling member toward and awayfrom the supporting frame, and compensating means for causing thehydraulic means to move the free end of the boom relative to thesupporting frame as the material handling member swings about the freeend of the boom in a direction such that the material handling membermoves toward and away from the supporting frame in a straight line path,said boom being pivotally movable relative to the supporting frame in agenerally upward and downward direction, said compensating means causingthe boom to move upwardly during downward movement of the materialhandling member relative to the free end of the boom and boom to movedownwardly during upward movement of the material handling memberrelative to the free end of the boom, said hydraulic means including apiston and cylinder boom actuator mounted between the supporting frameand boom. such that the piston extends from the cylinder when the boompivots downwardly and retracts into the cylinder when the boom pivotsupwardly, and wherein said compensating means controls the flow ofhydraulic fluid to the cylinder to cause the piston to retract into thecylinder as the material handling member moves downwardly relative tothe free end of the boom and causes the piston to extend from thecylinder as the material handling member moves upwardly relative to thefree end of the boom.

6. Material handling apparatus as defined in claim 5 wherein saidcompensating means comprises a compensating piston and cylinder actuatorhydraulically connected with the boom actuator such that extension andretraction of the compensating actuator causes retraction and extensionof the boom actuator, respectively, and a cam on the dipper stickengaged with the piston of the compensating actuator to cause extensionand retraction of the compensating actuator in accordance with theangular position of the dipper stick relative to the boom.

7. In material handling apparatus including a support, a bOOm having oneend pivotally mounted on the support, a dipper stick having one endpivotally mounted on the other end of the boom, a bucket pivotallymounted on the other end of the dipper stick, a boom actuator mountedbetween the boom and support for pivoting the boom about the support, adipper stick actuator between the boom and dipper stick for pivoting thedipper stick relative to the boom, and a bucket actuator between thebucket and the dipper stick for pivoting the bucket relative to thedipper stick, the improvement comprising compensating means for causingthe boom actuator to move said one end of the dipper stick vertically inaccordance with the angular position of the dipper stick relative to theboom independently of the angular position of the bucket relative to thedipper stick to cause the excavating bucket to move in a straight linepath without altering the angle between the dipper stick and bucket.

8. The construction claimed in claim 7 wherein said compensating meansincludes a compensating actuator on the boom operable to cause raisingand lowering of said other end of the dipper stick relative to thesupport, and means on the dipper stick engaging said actuator tocausethe actuator to raise said other end of the dipper stick during downwardtravel of the bucket relative to the other end of the dipper stick, andto lower the, other end of the dipper stick during upward travel of thebucket relative to said other end of the dipper stick.

References Cited UNITED STATES PATENTS 3,343,693 9/1967 Becker 214---138HUGO 0. SCHULZ, Primary Examiner.

